Cavitation catheter

ABSTRACT

In some examples, a catheter includes an elongated member including at least one balloon connected to the elongated member, the at least one balloon being configured to inflate to an expanded state. In the expanded state, the at least one balloon forms at least a portion of a cavity with a wall of a vessel of the patient. The catheter including at least one electrode carried by the elongated member and having at least one surface exposed to the cavity formed by the at least one balloon. The electrode is configured to connect to an energy source that is configured to deliver, via the electrode, an electrical signal to a fluid contained in the cavity and in contact with the electrode to cause the fluid to undergo cavitation to generate a pressure pulse wave within the fluid.

This application is a divisional of U.S. application Ser. No.16/661,517, filed on Oct. 23, 2019, and entitled, “CAVITATION CATHETER,”which claims the benefit of U.S. Provisional Application No. 62/750,456,filed on Oct. 25, 2018, and entitled, “CAVITATION CATHETER,” thecontents of each of which are incorporated by reference herein in theirentirety.

TECHNICAL FIELD

This disclosure relates to medical catheters.

BACKGROUND

Medical catheters have been proposed for use with various medicalprocedures. For example, medical catheters may be used to access andtreat defects in blood vessels, such as, but not limited to, treatmentof calcific atherosclerotic plaque buildup within the vasculature wallof vasculature associated with cardiovascular disease. Some techniquesfor treating such diseases may include balloon angioplasty alone orballoon angioplasty followed by stenting of the vasculature. However,such techniques may fail to address certain types of plaque buildupand/or result in re-stenotic events.

SUMMARY

In some aspects, the disclosure describes example medical devices, suchas catheters, that include one or more occlusion balloons and at leastone electrode configured to deliver energy intravascularly to fluid incontact with a vasculature wall to induce cavitation within the fluid.The cavitation may be used to treat a defect in the vasculature of thepatient. For example, the cavitation may produce a high-energy pressurepulse wave that, when directed at a vasculature wall, may be used todisrupt and fracture calcific atherosclerotic plaque buildup within thevasculature wall. The disruption and fracture of the plaque may allowthe vasculature to be more easily expanded to achieve better blood flowthrough the vessel. In some examples, the use of such devices may reduceor eliminate the need for subsequent stenting of the vasculature andreduce the chance of restenosis. In some other aspects, the disclosuredescribes methods of using the catheters described herein.

Clause 1: In one example, a catheter includes an elongated memberconfigured to be navigated though vasculature of a patient to a targettreatment site; a balloon connected to the elongated member, the balloonbeing inflatable to an expanded state to occlude a vessel of thepatient; and an electrode positioned around a portion of an exterior ofthe balloon, the electrode configured to electrically connect to anenergy source configured to deliver an electrical signal, via theelectrode, to a fluid in contact with the electrode to cause the fluidto undergo cavitation to generate a pressure pulse wave within thefluid, where, when the balloon is in the expanded state, the electrodeis configured to cause the balloon to form a first lobe and a secondlobe by restricting the expansion of the balloon, the first lobe and thesecond lobe being configured to form a cavity when the first lobe andthe second lobe contact a wall of the vessel in the expanded state.

Clause 2: In some of the examples of the catheter of clause 1, theelectrode includes a concentric electrode including an outerelectrically conductive band and an inner electrically conductive bandseparated by an electrically insulating layer, an aperture extendingthrough the outer electrically conductive band and the electricallyinsulating layer to provide fluid communication between the outer andthe inner electrically conductive bands.

Clause 3: In some of the examples of the catheter of clause 1 or 2, theelectrode includes a cylindrical body, the cylindrical body configuredto maintain a cylindrical shape when the balloon is inflated to theexpanded state.

Clause 4: In some of the examples of the catheter of any one of clauses1 to 3, where the electrode defines at least one surface exposed to thecavity.

Clause 5: In some of the examples of the catheter of any one of clauses1 to 4, the balloon includes a wrapped balloon including a plurality ofpleats, where, when the balloon is in a non-expanded state, the pleatsare wrapped around the elongated member.

Clause 6: In some of the examples of the catheter of clause 5, thecatheter includes an electrical conductor electrically coupled to theelectrode, the electrical conductor extending along the elongated memberand positioned along an exterior of the wrapped balloon.

Clause 7: In some of the examples of the catheter of clause 6, where,when the balloon is in the non-expanded state, at least one pleat of theplurality of pleats is folded over the electrical conductor.

Clause 8: In some of the examples of the catheter of clause 6, where,when the balloon is in the non-expanded state, the electrical conductoris positioned adjacent to an apex of at least one pleat of the pluralityof pleats.

Clause 9: In some of the examples of the catheter of any one of clauses1 to 8, the elongated member defines an inner lumen configured toreceive a guidewire.

Clause 10: In some of the examples of the catheter of any one of clauses1 to 9, the balloon defines at least one perfusion aperture configuredto supply a fluid to the cavity.

Clause 11: In some of the examples of the catheter of any one of clauses1 to 10, the balloon includes at least one of an anti-restenotic agent,an anti-proliferative agent, or an anti-inflammatory agent.

Clause 12: In some of the examples of the catheter of any one of clauses1 to 11, the electrode includes a first electrode and the cavityincludes a first cavity, the catheter further including a secondelectrode positioned around a distal portion of the exterior of theballoon, where, when the balloon is in the expanded state, the secondelectrode is configured to cause the balloon to form a third lobe andthe second lobe by restricting the expansion of the balloon, the secondlobe and the third lobe configured to form a second cavity containingthe second electrode when the second lobe and the third lobe contact thewall of the vessel in the expanded state.

Clause 13: In one example, a catheter includes an elongated memberconfigured to be navigated though vasculature of a patient to a targettreatment site; a first balloon connected to the elongated member, thefirst balloon being inflatable to an expanded state to occlude aproximal portion of a vessel proximal to the target treatment site; asecond balloon connected to the elongated member, the second balloonbeing inflatable to an expanded state to occlude a distal portion of thevessel distal to the target treatment site, and where when the first andsecond balloons are in the respective expanded states within the vessel,a cavity is defined between the elongated member and the targettreatment site, the cavity being exterior to the first and secondballoons; and an electrode including an electrically conductive bandattached to the elongated member, the electrode configured to beconnected to an energy source configured to deliver an electrical signalto a fluid within the cavity and in contact with the electrode to causethe fluid to undergo cavitation to generate a pressure pulse wave withinthe fluid.

Clause 14: In some of the examples of the catheter of clause 13, theelectrode includes a concentric electrode where the electricallyconductive band forms an outer electrically conductive band, theconcentric electrode further including an inner electrically conductiveband separated from the outer electrically conductive band by anelectrically insulating layer, an aperture extending through the outerelectrically conductive band and the electrically insulating layer toprovide fluid communication between the inner and the outer electricallyconductive bands.

Clause 15: In some of the examples of the catheter of clause 13, theelectrically conductive band forms a first electrically conductive bandon the elongated member, the first electrically conductive band having afirst surface area exposed to the cavity, the catheter further includinga second electrically conductive band on the elongated member, thesecond electrically conductive band having a second surface area exposedto the cavity, the first and the second electrically conductive bandsconfigured to deliver an electrical signal between the first and thesecond surface areas through the fluid within the cavity to cause thefluid to undergo cavitation.

Clause 16: In some of the examples of the catheter of clause 15, thefirst surface area and the second surface area are separated by adistance of at least about 2 mm.

Clause 17: In some of the examples of the catheter of any one of clauses13 to 16, the elongated member defines a lumen and at least one portconnecting the lumen to the cavity and the lumen and the at least oneport are configured to at least one of perfuse the cavity with the fluidor aspirate the cavity.

Clause 18: In some of the examples of the catheter of clause 17, thelumen and the at least one port are configured to perfuse the cavitywith the fluid and aspirate the cavity.

Clause 19: In some of the examples of the catheter of any one of clauses13 to 18, the elongated member the defines an inner lumen configured toreceive a guidewire.

Clause 20: In some of the examples of the catheter of any one of clauses13 to 19, where at least one of the first balloon or the second balloonincludes at least one of an anti-restenotic agent, an anti-proliferativeagent, or an anti-inflammatory agent.

Clause 21: In some of the examples of the catheter of any one of clauses13 to 20, further including an electrical wire that extends along theelongated member, a surface of the electrical wire being exposed withinthe cavity, the electrical wire configured to be connected to the energysource configured to deliver an electrical signal between the surface ofthe electrical wire and the electrode.

Clause 22: In some of the examples of the catheter of clause 21, where aplurality of surfaces of the electrical wire are exposed to the fluidwithin the cavity, each exposed surface of the plurality of exposedsurfaces forming an electrode.

Clause 23: In one example, a catheter includes an elongated memberconfigured to be navigated though vasculature of a patient to a targettreatment site; a first balloon connected to the elongated member, thefirst balloon being inflatable to an expanded state to occlude aproximal portion of a vessel proximal to the target treatment site; asecond balloon connected to the elongated member, the second balloonbeing inflatable to an expanded state to occlude a distal portion of thevessel distal to the target treatment site, and where when the first andsecond balloons are in the respective expanded states within the vessel,a cavity is defined between the elongated member and the targettreatment site, the cavity being exterior to the first and secondballoons; and an electrical wire that extends along the elongatedmember, the electrical wire defining a plurality of exposed surfaceswithin the cavity, each exposed surface of the plurality of exposedsurfaces forming a respective electrode, where the electrical wire isconfigured to be connected to an energy source configured to deliver anelectrical signal to a fluid within the cavity and in contact with theplurality of exposed surfaces to cause the fluid to undergo cavitationto generate a pressure pulse wave within the fluid.

Clause 24: In some of the examples of the catheter of clause 23, theelectrical wire includes a first electrical wire and the plurality ofexposed surfaces include a first plurality of exposed surfaces, thecatheter further including a second electrical wire that extends alongthe elongated member, the second electrical wire defining at least oneexposed surface within the cavity forming a return electrode, where thesecond electrical wire is configured to be connected to the energysource configured to deliver the electrical signal between the least oneexposed surface of the second electrical wire and the plurality ofexposed surfaces of the first electrical wire to cause the fluid toundergo cavitation.

Clause 25: In some of the examples of the catheter of clause 23 or 24,where adjacent exposed surfaces of the plurality of exposed surfaces areseparated by a distance of at least about 2 mm.

Clause 26: In some of the examples of the catheter of any one of clauses23 to 25, the elongated member defines a lumen and at least one portconnecting the lumen to the cavity, where the lumen and the at least oneport are configured to at least one of perfuse the cavity with the fluidor aspirate the cavity.

Clause 27: In some of the examples of the catheter of clause 26, thelumen and the at least one port are configured to perfuse the cavitywith the fluid and aspirate the cavity.

Clause 28: In some of the examples of the catheter of any one of clauses23 to 27, the elongated member the defines an inner lumen configured toreceive a guidewire.

Clause 29: In some of the examples of the catheter of any one of clauses23 to 28, where at least one of the first balloon or the second balloonincludes at least one of an anti-restenotic agent, an anti-proliferativeagent, or an anti-inflammatory agent.

Clause 30: In one example, a method includes introducing a catheterthrough vasculature of a patient to a target treatment site, thecatheter including an elongated member including a distal portionconfigured to be navigated though the vasculature of the patient; afirst balloon connected to the elongated member; a second balloonconnected to the elongated member and distal to the first balloon; andat least one electrode carried by the elongated member between the firstand second balloons. The method includes inflating the first and secondballoons to an expanded state, where the first balloon occludes aproximal portion of a vessel proximal to the target treatment site andthe second balloon occludes a distal portion of the vessel distal to thetarget treatment site, where the first and second balloons in therespective expanded states within the vessel form a cavity definedbetween the elongated member and the target treatment site, the cavitybeing exterior to the first and the second balloons; filling the cavitywith a fluid; and delivering energy to the fluid within the cavity usingthe at least one electrode to cause the fluid to undergo cavitation andgenerate a pressure pulse wave within the fluid.

Clause 31: In some of the examples of the method of clause 30, inflatingthe first and second balloons includes inflating the first balloon priorto inflating the second balloon.

Clause 32: In some of the examples of the method of clause 30, inflatingthe first and second balloons includes inflating the second balloonprior to inflating the first balloon.

Clause 33: In some of the examples of the method of clause 30, inflatingthe first and second balloons includes simultaneously inflating thefirst balloon and the second balloon.

Clause 34: In some of the examples of the method of any one of clauses30 to 33, delivering the electrical signal includes delivering aplurality of electrical pulses having a pulse width of about 1microsecond (μs) to about 200 (μs).

Clause 35: In some of the examples of the method of any one of clauses30 to 34, the method includes repositioning the catheter and inflatingthe first or the second balloon to expand the vessel after a pressurepulse wave therapy has been performed by the at least one electrode.

Clause 36: In some of the examples of the method of any one of clauses30 to 35, the method includes aspirating the cavity formed by the firstand second balloons after a pressure pulse wave therapy has beenperformed by the at least one electrode.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages of examples according to this disclosure will be apparentfrom the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of an example catheter, which includesan elongated member, the side view showing the catheter along alongitudinal axis of the elongated member.

FIG. 2 is an enlarged conceptual cross-sectional view of the distalportion of the catheter of FIG. 1 taken along the longitudinal axis ofthe elongated member.

FIGS. 3A and 3B are schematic side views of an example concentricelectrode that may be used with the catheter of FIG. 1.

FIGS. 4-6 illustrate additional examples of electrode configurationsthat may be incorporated as the electrode of the catheter of FIG. 1.

FIG. 7 is a schematic block diagram of an example cavitation energysource that may be used with the catheter of FIG. 1 to induce cavitationof within a fluid.

FIG. 8 is a schematic side view of another example catheter, the sideview showing the catheter along a longitudinal axis of the elongatedmember.

FIG. 9 is an enlarged conceptual cross-sectional view of a distalportion of the catheter of FIG. 8 taken the along longitudinal axis ofthe elongated member.

FIG. 10 is an example side view of the electrode of FIG. 9 taken throughline B-B.

FIGS. 11A-11C are schematic views of an example wrapped balloon in acollapsed state, which may be used as the balloon on the catheter ofFIG. 8.

FIG. 12 is a flow diagram of an example technique of using the cathetersdescribed herein.

DETAILED DESCRIPTION

This disclosure describes catheters, such as intravascular cathetersthat include a relatively flexible elongated member (e.g., the body ofthe catheter) configured to be navigated through vasculature of apatient to a target treatment site within the vasculature. The cathetersmay each include one or more occlusion balloons connected to theelongated member, the one or more balloons being configured to define acavity between the elongated member and a wall of a vessel when the oneor more balloons are in an expanded state. The catheter further includesone or more electrodes configured to deliver an electrical signal (e.g.,an electrical pulse) through the fluid captured in the cavity definedbetween (but external to) the one or more balloons and the vessel wall.The energy transmitted to the fluid may rapidly heat the fluid toproduce a short-lived gaseous steam/plasma bubble within the fluid thatquickly collapses (e.g., cavitates), releasing energy in the form of apressure pulse wave. The pulse wave may be used to treat a defect in thevasculature of the patient at the target treatment site.

In some examples, the target treatment site may be a site within thevasculature that has a defect that may be affecting blood flow throughthe vasculature. For example, the target treatment site may be a portionof the vasculature wall that includes a calcified lesion, e.g., calcificatherosclerotic plaque buildup. A calcified lesion can cause partial orfull blockages of blood bearing vasculatures, which can result inadverse physiological effects to the patient. Such lesions may be veryhard and difficult to treat using traditional methods, such as balloonangioplasty, stenting, thrombectomy, atherectomy, or otherinterventional procedures. The pressure pulse wave resulting from thecavitation procedure using a catheter described herein may impact thecalcified lesion (or other defect at the treatment site) to fracture ordisrupt at least part of the lesion. This treatment of the calcifiedlesion may be used in conjunction with a treatment balloon to helpopen-up the blood vessel of the patient, improving blood flow in theblood vessel. For example, the treatment of the calcified lesion usingthe catheters described herein may help restore the vasculature to anormal or at least increased flow diameter.

FIG. 1 is a schematic side view of an example catheter 10, whichincludes an elongated member 12 extending from proximal end 12A todistal end 12B. The side view of catheter 10 shown in FIG. 1 illustratescatheter 10 along a longitudinal axis 13 of elongated member 12.Catheter 10 includes a hub 14 connected to proximal end 12A of elongatedmember 12. Hub 14, including proximal end 12A of elongated member 12,forms part of a proximal portion 16A of catheter 10. Catheter 10 alsoincludes a distal portion 16B that includes distal end 12B of elongatedmember 12. The designations of proximal and distal portion 16A and 16Bare used to describe different regions of catheter 10 (as divided alonga length of catheter 10) and may be of any suitable length. In someexamples, elongated member 12 may also be characterized as having one ormore intermediate portions separating the proximal and distal portions16A and 16B.

Distal portion 16B of catheter 10 includes a first balloon 18 and asecond balloon 20 connected to elongated member 12. First and secondballoons 18 and 20 are configured to inflate to an expanded state toocclude a proximal and a distal portion of a vessel respectively to forma cavity 22 between first and second balloons 18 and 20. In someexamples, cavity 22 may be a closed cavity between first and secondballoons 18, 20, and a wall of a vessel of a patient (not shown in FIG.1). Distal portion 16B also includes at least one electrode 24 carriedby elongated member 12 and positioned between first and second balloons18 and 20. For example, as describe further below, electrode 24 may bemechanically connected to elongated member 12, integrally formed withelongated member 12, or the like. Electrode 24 includes at least onesurface exposed to a fluid received within cavity 22.

In some examples, catheter 10 may include a hub 14 positioned atproximal portion 16A. Proximal end 12A of elongated member 12 isreceived within hub 14 and can be mechanically connected to hub 14 viaan adhesive, welding, or another suitable technique or combination oftechniques. Hub 14 may include one or more supply tubes 26A, 26B, 26C,26D (collectively “supply tubes 26”). Supply tubes 26 may provide accessto the various components of distal portion 16B of elongated member 12and may be used for accessing or transporting various components throughelongated member 12 (e.g., a guidewire, fluids, electrical conductors,aspiration force, or the like). For example, one or more of supply tubes26 may define a lumen that extends through elongated member 12 to one orboth of first balloon 18 and second balloon 20, and a fluid may beintroduced through the lumen to inflate the balloons 18, 20 to anexpanded state that occludes a vessel of a patient. Additionally, oralternatively, one or more of supply tubes 26 may be used toelectrically connect electrode 24 to an energy source (e.g., energysource 70 of FIG. 7); used to perfuse or aspirate cavity 22; used tointroduce a guidewire into a lumen of elongated member 12; and the like.

In some examples, catheter 10 may include a strain relief body (notshown), which may be a part of hub 14 or may be separate from hub 14.The strain relief body may extend distally from hub 14 and may helpreduce mechanical strain between hub 14 and elongate member 12.Additionally, or alternatively, proximal portion 16A of catheter 10 caninclude another structure in addition or instead of hub 14. For example,catheter hub 14 may include one or more luers or other mechanisms forestablishing mechanical connections, fluidic connections, or other typesof connections between catheter 10 and other devices.

In some examples, elongated member 12 of catheter 10 may be used toaccess relatively distal vasculature locations in a patient or otherrelatively distal tissue sites (e.g., relative to the vasculature accesspoint). Example vasculature locations may include, for example,locations in a coronary artery, peripheral vasculature (e.g., carotid,iliac, or femoral artery, or a vein), cerebral vasculature, or a heartvalve (e.g., aortic valve, mitral valve, tricuspid valve, or the like).In some examples, elongated member 12 is structurally configured to berelatively flexible, pushable, and relatively kink- andbuckle-resistant, so that it may resist buckling when a pushing force isapplied to proximal portion 16A of catheter 10 to advance elongatedmember 12 distally through vasculature, and so that it may resistkinking when traversing around a tight turn in the vasculature. Unwantedkinking and/or buckling of elongated member 12 may hinder a clinician'sefforts to push the catheter body distally, e.g., past a turn in thevasculature.

Elongated member 12 has a suitable length for accessing a target tissuesite within the patient from a vasculature access point. The length maybe measured along the longitudinal axis of elongated member 12. Theworking length of elongated member 12 may depend on the location of thelesion within vasculature. For example, if catheter 10 is a catheterused to access a coronary, carotid, or abdominal artery, elongatedmember 12 may have a working length of about 50 centimeters (cm) toabout 200 cm, such as about 110 cm, although other lengths may be used.In other examples, or for other applications, the working length ofelongated member 12 may have different lengths.

The outer diameter of elongated member 12 may be of any suitable size ordimension including, for example, between about 1 millimeter (mm) andabout 12 mm. In some examples, the outer diameter may be substantiallyconstant (e.g., uniform outer diameter), tapered (e.g. tapered or stepchange to define a narrower distal portion), or combinations thereof. Insome examples, elongated member 12 of catheter 10 may have a relativelysmall outer diameter which may make it easier to navigate through atortuous vasculature.

In some examples, at least a portion of an outer surface of elongatedmember 12 may include one or more coatings, such as, but not limited to,an anti-thrombogenic coating, which may help reduce the formation ofthrombi in vitro, an anti-microbial coating, and/or a lubricatingcoating. In some examples, the entire working length of elongated member12 is coated with the hydrophilic coating. In other examples, only aportion of the working length of elongated member 12, e.g., includingdistal portion 16B, may be coated with the hydrophilic coating. This mayprovide a length of elongated member 12 distal to hub 14 that does notinclude a hydrophilic coating and with which the clinician may gripelongated member 12, e.g., to rotate elongated member 12 or pushelongated member 12 through vasculature. In some examples, the entireworking length of elongated member 12 or portions thereof may include alubricious outer surface, e.g., a lubricious coating. The lubricatingcoating may be configured to reduce static friction and/or kineticfriction between elongated member 12 and tissue of the patient aselongated member 12 is advanced through the vasculature.

In some examples, elongated member 12 may include one or more radiopaquemarkers which may help a clinician determine the positioning ofelongated member 12 relative to a target treatment site. For example,one or more radiopaque markers may be positioned proximal or distal tofirst balloon 18, proximal or distal to second balloon 20, in betweenfirst and second balloon 18 and 20, adjacent to electrode 24, orcombinations thereof. In some examples, portions of electrode 24 itselfmay be radiopaque.

FIG. 2 is an enlarged conceptual cross-sectional view of distal portion16B of catheter 10 of FIG. 1 taken along longitudinal axis 13 ofelongated member 12. FIG. 2 shows distal portion 16B deployed withinvessel 30 of a patient. Vessel 30 includes a target treatment site 32containing a calcified lesion 34 on or within a wall of vessel 30. Thelocation of lesion 34 in FIG. 2 is one example, and lesion 34 may behave another location on or within the vessel wall in other examples. Insome examples, lesion 34 may be superficial or a deep calcificationwithin the tissue of vessel 30. Additionally, or alternatively, lesion34 may be on or within a heart valve (e.g., aortic valve).

Distal portion 16B of elongated member 12 includes first balloon 18 andsecond balloon 20 mechanically connected to elongated member 12. Firstballoon 18 is mechanically connected to elongated member 12 at aposition proximal to second balloon 20. Thus, first balloon 18 may bereferred to as a proximal balloon and second balloon 20 may be referredto as a distal balloon.

Balloons 18 and 20 are each configured to be expanded from a deflatedstated to an expanded state via an inflation fluid delivered to therespective balloon via an inflation lumen (not shown) of elongate body12, which may be accessed via one or more of supply tubes 26 (FIG. 1).In some examples, inflating first and second balloons 18 and 20independently may useful to ensure each balloon is expanded properly toconform to the contours of the vessel 30. Additionally, as discussedfurther below, inflating first and second balloons 18 and 20independently may allow for blood between first and second balloons 18and 20 to be removed prior to both balloons being fully expanded. Inother examples of catheter 10, first and second balloons 18 and 20 canbe inflated via the same inflation lumen or separate inflation lumens.

In the respective expanded states within vessel 30, first and secondballoons 18 and 20 inflate and conform to engage with the wall of vessel30. First balloon 18 engages with vessel 30 at a position proximal totarget treatment site 32 to prevent blood from flowing through vessel 30during a cavitation procedure and second balloon 20 engages with vessel30 at a position distal to target treatment site 32 and occludes vessel30. In some examples, catheter 10 including at least two shorterballoons 18 and 20 may improve deliverability of catheter 10 relative toa catheter including a longer balloon (e.g., longer than the combinedlength of the balloons 18, 20 or longer than one of the balloons 18,20). For example, when catheter 10 is configured for use in someprocedures, such as some coronary cavitation procedures, first andsecond balloons 18 and 20 may be relatively short (e.g., about 3 mm toabout 4 mm) compared to a single balloon extending over all ofelectrodes 24. The respective length of the balloons may improvedeliverability and engagement with vessel 30, particularly in exampleswhere vessel 30 is tortuous. For example, balloons 18, 20 may engagewith different portions of the vessel 30 when inflated, rather thanengaging with a continuous length of vessel 30. This may help reduce,for example, strain on a curved vessel 30. Further, two balloons 18, 20may increase a flexibility of catheter 10 (compared to a catheterincluding a single longer balloon), thereby increasing an ease ofdelivery of catheter 10 through vessel 30 as well as the flex ofcatheter 10 when balloons 18, 20 are inflated within a curved vessel 30.

In addition, in some examples, by configuring catheter 10 such thatfirst and second balloons 18 and 20 can inflate independently, theballoons may reduce the strain or torque on vessel 30 when inflatedcompared to a longer balloon, e.g., having a length equal to a combinedlength of balloons 18, 20. Relatively shorter balloons may help mitigateadverse effects on vessel 30 if the balloons are inflated at a bend invessel 30

Collectively in their expanded states, first and second balloons 18 and20 create cavity 22 adjacent to target treatment site 32 that can befilled with a conductive fluid (e.g., blood or saline) used for thecavitation procedure. In their expanded states, first and secondballoons 18 and 20 may also help center electrode 24 within vessel 30,which may help ensure a more equal distribution of the pressure pulsewave against the wall of vessel 30 during the cavitation process as wellas reduce the chance of localized heating along the wall of vessel 30 byelectrode 24.

First and second balloons 18 and 20 may each be formed from any suitablematerial, such as a flexible polymeric material that is configured toform a tight seal with elongated member 12. In some examples, first andsecond balloons 18 and 20 may be formed physically separate fromelongated member 12 and attached to an exterior surface of elongatedmember 12 via co-extrusion, bonding, adhesives, or the like. In otherexamples, first and second balloons 18 and 20 may be integrally formedwith elongated member 12 such that one or both balloons 18, 20 areembedded or at least partially embedded in elongated member 12. In someexamples, first and second balloons 18 and 20 may be constructed using aflexible polymeric material including, for example, nylon 12,polyethylene, polyethylene terephthalate (PET), silicone, polyvinylchloride, polypropylene, polyurethanes, polyamides, polyesters, latex,natural rubber, synthetic rubber, polyether block amides, or the like.Additionally, or alternatively first and second balloons 18 and 20 maybe constructed with an electrically insulative material.

In some examples, first and second balloons 18 and 20 may be configuredto be deflatable via a vacuum or other stable source to forcibly removefluid from the balloon, thereby allowing for quicker collapse and/or alower cross-sectional profile after the cavitation procedure iscompleted. Additionally, or alternatively, first and second balloons 18and 20 may include one or more perfusion ports allowing fluid tocontinuously flow from the balloon into vessel 30.

First and second balloons 18 and 20 may have any suitable size or shape.In some examples, first and second balloons 18 and 20 may have the samesize and/or shape, while in other examples first and second balloons 18and 20 may have different sizes and/or shapes. Constructing catheter 10to include balloons of different sizes or shape may be useful wherecatheter 10 is disposed within a vessel with an irregular configurationor disposed adjacent to a heart valve (e.g., aortic valve). For example,first or second balloons 18 and 20 may be sized and configured to anchorin the heart valve for use in procedures in which catheter 10 is used totreat calcified lesion in or near the heart valve. In some suchexamples, first and second balloons 18 and 20 may define a crosssectional diameter of about 30 mm to about 80 mm in the expanded statesso that the balloons anchor on different sides of the heart valve withthe valve being positioned within cavity 22. In examples in whichcatheter 10 is configured for use in a coronary cavitation procedure,first and second balloons 18 and 20 may define a cross sectionaldiameter in the expanded state equal to or greater than thecross-sectional diameter of vessel 30 (e.g., on the order of about 2 mmto about 4 mm). Additionally, or alternatively, first and secondballoons 18 and 20 may exhibit a cross sectional diameters that isconfigured to conform to a range of vessel diameters when inflated tothe expanded state.

First and second balloons 18 and 20 may also have any suitable length(measured along longitudinal axis 13) which may depend, for example, onthe length of calcified lesion 34 or the size and shape of vessel 30.For some procedures used to treat calcifications in or near a heartvalve (e.g., aortic valve) of a patient, first and second balloons 18and 20 may each define a length of about 5 mm to about 30 mm with atotal length (including the length of cavity 22) of about 15 mm to about100 mm. For some procedures used to treat calcifications in or near thecoronary vasculature, first and second balloons 18 and 20 may define alength of about 1 mm to about 4 mm. First and second balloons 18 and 20may also be separated by any suitable length along longitudinal axis 13so that the target treatment site 32 is positioned within cavity 22. Insome examples, the length of cavity 22 measured along longitudinal axis13 (e.g., the distance between first and second balloons 18 and 20) maybe about 5 mm to about 40 mm.

When both first and second balloons 18 and 20 are inflated to therespective expanded states and engage with vessel 30, first and secondballoons 18 and 20 form cavity 22. In some examples, cavity 22 may be aregion created by the wall of vessel 30, the exterior surfaces of firstand second balloons 18 and 20 when first and second balloons 18 and 20are inflated in vessel 30, and any region (if any) of elongated member12 separating first and second balloons 18 and 20. Fluid 36 may becontained within cavity 22 by the vessel wall 36 and the exteriorsurfaces of first and second balloons 18 and 20 such that fluid 36 liesin direct contact with vessel wall 36. In some examples, cavity 22 maydefine a tubular shape that encircles part of the exterior surface ofdistal portion 16B, limited by first and second balloons 18 and 20 andvessel wall 36.

Cavity 22 may be filled with a fluid 36 capable of undergoing cavitationvia energy delivered to fluid 36 by electrode 24. In some examples,fluid 36 may be or include residual blood within vessel 30 confinedwithin cavity 22 by first and second balloons 18 and 20. In addition toor instead of the residual blood, in some examples, fluid 36 may be orotherwise include a fluid introduced into cavity 22, such as, but notlimited to, saline. In these examples, fluid 36 includes fluid not foundin the patient's body, but, rather, introduced into cavity 22 by aclinician. In examples in which fluid 36 is introduced into cavity 22,fluid 36 may be introduced into cavity 22 using any suitable technique.In some examples, elongated member 12 may define one or more lumens 38configured to provide access to cavity 22. Lumen 38 may permit thedelivery of fluid 36, such as saline, into cavity 22 via one of supplytubes 26 and access ports 40 defined by elongated member 12.

In some examples, lumen 38 and access ports 40 may be used to perfusecavity 22 with fluid 36 during the cavitation procedure. The perfusionof fluid 36 may help resupply fluid to cavity 22 that is lost due toleakage across one or more of first and second balloons 18 and 20.Additionally, or alternatively, the perfusion of fluid 36 into cavity 22during the cavitation procedure may help dissipate heat within cavity 22generated during the cavitation process.

Any suitable fluid 36 may be introduced into cavity 22 for thecavitation procedure. Example fluids 36 may include, but are not limitedto, biocompatible fluids such as saline, phosphate buffered saline(PBS), or similar solution with a salt content between about 0.9 weightpercent (wt. %) and about 5 wt. %; contrast media (e.g., about 25 volumepercent (vol. %) to about 75 vol. % contrast media), or the like. Salineor other ionic solutions may more readily undergo cavitation compared toblood, thereby requiring less energy to induce cavitation within fluid36 in cavity 22. For example, the higher the salt content of the salinefluid, the higher the conductance will be for the fluid, therebyrequiring less energy to increase the temperature of the fluid andinduce cavitation. Additionally, the higher the concentration ofcontrast media, the more viscous fluid 36 will be leading to a higherdissipation of the cavitation bubbles. In some examples, fluid 36 may beheated (e.g., body temperature or about 37° C.) prior to introductioninto cavity 22. Heating fluid 36 may increase the relative vaporpressure of the fluid and thus require less energy to induce cavitation.

In some such examples, lumen 38 and access port 40 may also beconfigured to aspirate cavity 22 to remove blood, fluid 36 (e.g., pre-or post-cavitation), or other materials as part of the cavitationprocedure. For example, a vacuum source may be connected to one ofsupply tubes 26 to cause a fluid within cavity 22 to be suctioned fromthe cavity via lumen 38 and access port 40. Additionally, oralternatively, elongated member 12 may define a different lumen (e.g., alumen other than lumen 38 of FIG. 2) with access to cavity 22 forpurposes of aspirating cavity 22, or catheter 10 may be used inconjunction with an aspiration catheter.

In some examples, cavity 22 may be perfused with fluid 36 and aspiratedmultiple times during the cavitation procedure to remove any unwantedmaterial from cavity 22. For example, catheter 10 may include adedicated lumen to supply fluid 36 to cavity 22 and a separate lumendedicated to aspirating cavity 22. During the cavitation procedure,cavity 22 may be filled with fluid 36 and cavitated via energy deliveredby electrode 24, then fluid 36 (along with any debris of calcifiedlesion 34) may be removed from cavity 22 via aspiration and fresh fluid36 supplied to cavity 22. The entire procedure may then be repeateduntil calcified lesion 34 has been sufficiently treated.

Distal portion 16B of catheter 10 also includes at least one electrode24 configured to deliver energy to fluid 36 within cavity 22 to causefluid 36 to undergo cavitation. The term electrode may refer to thecomponent(s) or portions of the component(s) that are used to inducecavitation within cavity 22 and is not intended to imply that the entirecavitation system is included in cavity 22. For example, while electrode24 may refer to one or more portions of a conductor(s), marker band(s),or the like positioned in cavity 22, it is understood that the energysource for such componentry may not be located within cavity 22 and maybe exterior to the body of a patient.

During the cavitation procedure, energy in the form of, for example, anelectrical signal (e.g., electrical pulse) may be delivered to fluid 36via electrode 24 to heat a portion of fluid 36 to generate asteam/plasma bubbles within fluid 36. The steam/plasma bubbles mayrepresent relatively low-pressure pockets of vapor generated from thesurrounding fluid 36. The low-pressure steam/plasma bubbles eventuallycollapse in on themselves due to the relatively high pressure of thesurrounding fluid 36 and heat loss of the steam/plasma bubbles to thesurrounding fluid 36. As the steam/plasma bubbles collapse, the bubblesrelease a large amount of energy in the form of a high-energy pressurepulse wave within fluid 36. In some examples, the formation andsubsequent collapse of the steam/plasma bubbles may be short lived ornearly instantaneous, causing the pressure pulse waves to originate nearthe source of energy delivered to fluid 36 by electrode 24.

The pressure pulse waves may propagate through fluid 36 where theyimpact the wall of vessel 30 transmitting the mechanical energy of thepressure pulse wave into the tissue of vessel 30 and calcified lesion 34on or within the vessel wall. The energy transmitted to calcified lesion34 may cause the lesion to fracture or break apart allowing vessel 30 tobe subsequently expanded (e.g., via first or second balloon 18 or 20 ora different expansion balloon using balloon angioplasty (e.g., plain oldballoon angioplasty or POBA)) to a larger flow diameter.

By conducting the cavitation procedure in vessel 30 within fluid 36 indirect and intimate contact with the wall of vessel 30, the transfer ofenergy from the pressure pulse waves to calcified lesion 34 may be moreefficient as compared to a cavitation procedure that introduces one ormore intermediate devices, such as a sidewall of a balloon that mayotherwise dampen the pulse energy, between the source of cavitation(e.g., electrode 24) and calcified lesion 34. In some examples, theimproved efficiency of the process may require less energy to betransmitted to fluid 36 to incur the same amount of cavitation forces.Further, as the temperature of fluid 36 will increase as a consequenceof the cavitation procedure, reducing the overall energy delivered tofluid 36 may also help reduce the temperature increase to fluid 36caused by the delivery of energy to fluid 36. The more efficienttransfer of energy from the pressure pulse waves to calcified lesion 34may also reduce the duration that the cavitation procedure must beperformed in order to sufficiently fracture or break apart calcifiedlesion 34 resulting in an overall shorter procedure. In some examples,by cavitating fluid 36 within cavity 22, the space provided by cavity 22may allow for the resultant plasma bubbles to grow before collapsingwhich may help increase the resultant pressure created by the pressurepulse waves.

Additionally, or alternatively, due to the improved efficiency of thecavitation process, the profile of catheter 10 may be reduced. Forexample, the lower power requirements may mean that the componentspowering electrode 24 (e.g., the conductors supplying electrode 24) mayrequire a lower energy load thereby allowing for smaller gauge ofcomponents to be incorporated into catheter 10. In some examples, thelowered power demands may also permit catheter 10 and the associatedenergy source to be operated as a handheld unit.

Electrode 24 may include any suitable device configured to deliverenergy to fluid 36 within cavity 22 to cause fluid 36 to undergocavitation. In some examples, electrode 24 may include both a supply orpositive terminus and return or negative terminus to allow for thedelivery of electrical energy through fluid 36 to induce cavitation. Forexample, as shown in the example of FIG. 2, electrode 24 may include aconcentric electrode. FIGS. 3A and 3B are schematic side views of anexample concentric electrode 24A that may be used with catheter 10. FIG.3A illustrates an example side view of concentric electrode 24A and FIG.3B illustrates an example cross sectional view of concentric electrode24A taken through line A-A of FIG. 3A.

Concentric electrode 24A may include an inner and outer conductive band42 and 44 respectively separated by an electrically insulative layer 46(e.g., fluorinated ethylene propylene (FEP)). Inner and outer conductivebands 42 and 44 may each be electrically coupled to a respectiveelectrical conductor 48 and 50 extending along elongated member 12. Anelectrode aperture 52 may pass through outer conductive band 44 andelectrically insulative layer 46 to provide fluid communication betweeninner and outer conductive bands 42 and 44 (e.g., via fluid 36). Thatis, outer conductive band 44 and electrically insulative layer 46 maytogether define electrode aperture 52. Conductive bands 42 and 44 mayhave any suitable length to permit coupling to electrical conductors 48and 50. In some examples, each conductive band 42 and 44 may comprise aring or cylindrical body that defines a longitudinal length of about 1mm. In some examples, conductive bands 42 and 44 may be formed from amarker band, hypotube, or other suitable device.

During a cavitation procedure, an electrical signal (e.g., an electricalpulse) may be delivered between inner and outer conductive bands 42 and44 using fluid 36 captured within electrode aperture 52 to inducecavitation of fluid 36. The electrical signal transmitted may form acorona, an electrical arc, a spark, or the like between the pair ofinner and outer conductive bands 42 and 44 using fluid 36 as theconductive media. In some examples, outer conductive band 44 mayrepresent the return electrode such that the current density along theexposed surface area of inner conductive band 42 is maximized.Additionally, or alternatively, the exposed surface areas of innerconductive band 42 and outer conductive band 44 may be relatively smallto maximize the current density. In some examples, the size or materialof respective electrical conductors 48 and 50 may selected toaccommodate the desired current density inner and outer conductive bands42 and 44.

Electrode aperture 52 may take on any suitable shape and size. In someexamples, the size and shape of electrode aperture 52 may guide thedirection or size of the acoustic output of the pressure pulse waves. Insome examples, electrode apertures 52 of neighboring electrodes 24 maybe oriented in different circumferential directions along elongatedmember 12. Cavitation generated at the exposed surfaces of the electrodeapertures 52 may then produce pressure pulse waves directed in differentcircumferential directions within vessel 30. In some examples, electrodeaperture 52 may be in the shape of a ring around elongated member 12.

The electrical signal transmitted and received between inner and outerconductive bands 42 and 44 may be delivered from an energy sourceseparate from catheter 10 (e.g., energy source 70 of FIG. 7) usingelectrical conductors 48 and 50. Electrical conductors 48 and 50 mayextend from proximal portion 16A of catheter 10 to electrode 24A. Aproximal end of electrical conductors 48 and 50 may be electricallyconnected to the external energy source in order to electrically connectelectrode 24A to the energy source. For example, the proximal end ofconductors 48 and 50 may extend through one or more of supply tubes 26or may be connected to electrical contacts at or near proximal end 16Aof catheter 10. The electrical contacts may then be directlyelectrically connected to the energy source or electrically connected tothe energy source via a lead or another suitable electrical conductor.

While only a single electrode 24, 24A is illustrated in FIGS. 2 and 3B,catheter 10 may include a plurality of electrodes 24 each exposed tofluid 36 within cavity 22. In some examples, the number of electrodes 24included on catheter 10 may depend on the size and shape of calcifiedlesion 34. For example, for longer lesions 34, more electrodes 24 may beused to induce cavitation of fluid 36 along the entire length the lesion34 without needing to reposition catheter 10 during the procedure. Inexamples where concentric electrodes 24A are incorporated, eachconcentric electrode 24A may be separated by a distance of about 2 mm to5 mm along longitudinal axis 13 to prevent shorting between neighboringelectrodes.

FIGS. 4-6 illustrate additional examples of electrode configurationsthat may be incorporated as electrode 24 of catheter 10. FIG. 4 is aside view of a pair of conductive bands 54A and 54B (collectively“conductive bands 54”) at different longitudinal positions alongelongated member 12. Conductive bands 54 may be powered by electricalconductors 48 and 50 respectively. In such examples, catheter may beconsidered to include at least two electrodes 24 (e.g., conductive bands54A and 54B). While only two conductive bands 54 are shown in FIG. 4,catheter 10 may include any suitable number of conductive bands 54spaced along the length of elongated member 12. Each conductive band 54Aand 54B may include at least one exposed surface 56A and 56B to fluid 36within cavity 22 that is electrically conductive.

In some examples, conductive bands 54 may include at least oneconductive band (e.g., conductive band 54A) operating as a supply orpositive electrode and another conductive band (e.g., conductive band54B) operating as a return or negative electrode. In such examples, theelectrical signal delivered by the energy source may be deliveredbetween the conductive bands 54A and 54B as an arc or corona using fluid36 as the conductive medium. The separation distance between conductivebands 54A and 54B along a longitudinal axis 13 may determine whether theelectrical signal is delivered as an arc or corona. In examples in whichan arc discharge is desired, exposed surfaces 56A and 56B of conductivebands 54A and 54B may be separated by less than about 0.5 mm. Inexamples in which a corona discharge is desired, exposed surfaces 56Aand 56B of conductive bands 54A and 54B may be separated by the samedistance (e.g., less than about 0.5 mm) or a much greater distance(e.g., separated by a distance of about 1 mm to about 5 mm). The totalnumber of conductive bands 54 may be chosen depending on the size oflesion 34 at the target treatment site and the type of electrical signaldelivery desired.

Each conductive band 54A and 54B may include at least one exposedsurface 56A and 56B to fluid 36 within cavity 22 that provides alocation for where the cavitation can occur. In some examples, an outerjacket may be heat shrunk over conductive bands 54A and 54B with aportion of the outer jacket being removed (e.g., laser or mechanicallyetched or otherwise cut) to form each of exposed surfaces 56A and 56B.Each exposed surface 56A and 56B may define a respective electrodewithin cavity 22. An electrical signal can be delivered between theexposed surfaces 56A and 56B of conductive bands 54A and 54B by treatingone as a source electrode (e.g., positive terminus) and the other as thereturn electrode (e.g., negative terminus) to induce cavitation of fluid36. The site for cavitation may be controlled by controlling the surfacearea and/or materials of exposed surfaces 56A and 56B. The electrodewith the smaller surface area may have a higher current density andtherefore act as the site for cavitation to occur. Additionally, oralternatively, the direction of the resultant pressure pulse wavesproduced by the cavitation may be controlled based on thecircumferential location of exposed surfaces 56A and 56B along elongatedmember 12. In some examples, exposed surfaces 56A and 56B may beoriented in different circumferential directions alone elongated member12 to allow for 360° deployment of the pressure pulse waves withinvessel 30. Additionally, or alternatively, the positioning of exposedsurfaces 56A and 56B at different circumferential orientations alongelongated member 12 may allow for the electrical signal transmittedbetween the electrodes to “walk” circumferentially around elongatedmember 12.

In some examples, elongated member 12 may include a plurality ofconductive bands 54 electrically coupled to electrical conductors 48 and50 in an alternating fashion or supplied by their own independentelectrical conductor. Such configurations may allow for the electricalsignal to be passed between adjacent pairs of conductive bands 54 usingelectrical conductors 48 and 50 or between selected conductive bands 54respectively to induce cavitation at desired locations within cavity 22.

FIG. 5 is a cross-sectional view of another example electrodeconfiguration, which is an example of electrode 24 (FIG. 1) that may beused with catheter 10. In the example electrode configuration of FIG. 5,electrical conductors 48 and 50 extend along elongated body 12 with atleast one portion of each conductor 48 and 50 being exposed (e.g.,expose surfaces 58 and 60 respectively) to fluid 36 within cavity 22.For example, electrical conductors 48 and 50 may represent electricalwires extending within the body (e.g., imbedded or within an innerlumen) of elongated member 12. The wires may be braided, coiled, orlinearly extending along elongated member 12. In some examples, thewires may contribute or form part of the support structure of elongatedmember 12. Electrical conductors 48 and 50 may be electrically insulatedfrom one another by an insulating sheath or by the body of elongatedmember 12 which may be comprised of non-conductive material (e.g., FEP).Each electrical conductors 48 and 50 may define at least one exposedsurface 58 and 60 that allows electrical conductors 48 and 50 to be indirect contact with fluid 36. Exposed surfaces 58 and 60 of electricalconductors 48 and 50 may be formed by removing parts of elongated member12 (e.g., laser etching) to expose electrically conductive surfaces 58and 60 of conductors 48 and 50, respectively. Each exposed surface 58and 60 may act as a respective electrode within cavity 22. During acavitation procedure, an electrical signal can be delivered between oneor more of the exposed surfaces 58 and 60 of conductors 48 and 50 toinduce cavitation of fluid 36 in contact with both surfaces 58 and 60.

FIG. 6 is a cross-sectional view of another example electrodeconfiguration that may be used with catheter 10. Similar to theelectrode configuration of FIG. 5, electrical conductors 48 and 50extend along elongated body 12 with at least one portion of eachconductor 48 and 50 being exposed (e.g., exposed surfaces 62 and 64respectively) to fluid 36 within cavity 22. In some examples, theexposed surface 62, 64 of one or both of conductors 48 and 50 may beformed by passing the respective conductor (e.g., conductor 48 in FIG.6) along an exterior of elongated member 12. In such examples, theportion of the respective conductor extending along the exterior ofelongated member 12 (e.g., exposed surface 62 of conductor 48 in FIG. 6)may be exposed to fluid 36 within cavity 22. Each exposed surface 62 and64 may be characterized as an electrode within cavity 22. During thecavitation procedure, an electrical signal can be delivered between oneor more of the exposed surfaces 62 and 64 of conductors 48 and 50 toinduce cavitation of fluid 36 in contact with both surfaces 62 and 64.

In any of the above electrode configurations one or more access ports 40may be used to introduce fluid 36 into cavity 22. In some examples, oneor more of conductors 48 and 50 may share a common lumen that suppliesfluid 36 to cavity 22. In some such examples, one or more of the accessports 40 permitting entrance of fluid 36 into cavity 22 may also be thelocation where electrical conductor 48 and/or 50 is also exposed tofluid 36 in the cavity.

Components of electrode 24 and including, for example, conductors 48 and50 and/or conductive bands 44, 46, and 54 may be formed using anysuitable electrically conductive material including, for example,titanium alloys (e.g., Ti—Mo alloy), platinum or platinum-iridiumalloys, stainless steel, copper, copper alloys (e.g., copper and hafniumor tungsten), tungsten, or the like. In some examples, conductors 48 and50 and conductive bands 44, 46, and 54 (where used) may be formed of thesame material, while in other examples the components may be formed ofdifferent materials. In some examples, conductors 48 and 50 may beformed using metal wires extending along longitudinal axis 13 ofelongated member 12. Portions of the metal wires may be exposed to fluid36 via etching or other mechanism. In other examples, conductive bands44, 46, and 54 may be formed separate from conductors 48 and 50 andelectrically and mechanically connected to conductors 48 and 50.

In some examples, elongated member 12 may define a guidewire lumen(e.g., lumen 38) configured to receive a guidewire (not shown) used tohelp navigate distal portion 16B to target treatment site 32. Forexample, the guidewire may be introduced through vasculature of apatient to target treatment site 32 and distal portion 16B of catheter10 may be advanced over the guidewire to navigate elongated member 12through the vasculature of the patient to target treatment site 32.

In some examples, the intensity of the pressure pulse waves may beadjusted by controlling the intensity of the electrical signal deliveredvia electrodes 24, the separation distance between electrodes 24, theexposed surface area of the respective electrode 24, and the like. Theintensity of the electrical signal may be function of one or more of avoltage, a current, a frequency (e.g., a pulse rate in the case ofpulses), a pulse width, or one or more other electrical signalparameters.

In other examples, one of the electrodes associated with the cavitationprocedure (e.g., the reference electrode) may be external to thepatient. For example, catheter 10 may include electrode 24 positionedwithin vessel 30 of the patient and the reference or return electrodemay be positioned on the external skin surface of the patient, e.g., asa pad electrode. The electrical signal may be delivered between theelectrodes, through fluid 36 and the tissue of the patient to inducecavitation of fluid 36 at electrode 24.

FIG. 7 shows a schematic block diagram of an example energy source 70that may be used with catheter 10 to induce cavitation within fluid 36.Energy source 70 includes control mechanism 72, memory 74, processingcircuitry 76, electrical signal generator 78, and power source 80.

Processing circuitry 76 may include any one or more microprocessors,controllers, digital signal processors (DSPs), application specificintegrated circuits (ASICs), field-programmable gate arrays (FPGAs),discrete logic circuitry, or any processing circuitry configured toperform the features attributed to processing circuitry 76. Thefunctions attributed to processors described herein, includingprocessing circuitry 76, may be provided by a hardware device andembodied as software, firmware, hardware, or any combination thereof. Insome examples, processing circuity 76 may include instructions torecognize a particular electrode 24 configuration or allow a clinicianto manually input the specific electrode 24 configuration of catheter10. In some examples, energy source 70 may include additional componentssuch as, a display device or user input device that are not expresslyshown for displaying information from processing circuitry 76 orallowing the clinician to input information.

Memory 74 may include any volatile or non-volatile media, such as arandom access memory (RAM), read only memory (ROM), non-volatile RAM(NVRAM), electrically erasable programmable ROM (EEPROM), flash memory,and the like. Memory 74 may store computer-readable instructions that,when executed by processing circuitry 76, cause processing circuitry 76to perform various functions described herein. Memory 74 may beconsidered, in some examples, a non-transitory computer-readable storagemedium including instructions that cause one or more processors, suchas, e.g., processing circuitry 76, to implement one or more of theexample techniques described in this disclosure. The term“non-transitory” may indicate that the storage medium is not embodied ina carrier wave or a propagated signal. However, the term“non-transitory” should not be interpreted to mean that memory 74 isnon-movable. As one example, memory 74 may be removed from energy source70, and moved to another device. In certain examples, a non-transitorystorage medium may store data that can, over time, change (e.g., inRAM).

Processing circuitry 76 is configured to control energy source 70 andelectrical signal generator 78 to generate and deliver the electricalsignal across one or more electrodes 24 to induce cavitation of fluid36. Electrical signal generator 78 includes electrical signal generationcircuitry and is configured to generate and deliver an electrical signalin the form of pulses and/or a continuous wave electrical signal. In thecase of electrical pulses, electrical signal generator 78 may beconfigured to generate and deliver pulses having an amplitude of about500 volts (V) to about 5000 V (e.g., between about 1500 V to about 3000V), a pulse width of about 1 microsecond (μs) to about 5 μs for arc-typecavitation or about 10 μs to about 200 μs for corona-type cavitation,and a frequency of about 0.5 Hertz (Hz) to about 1000 Hz. In someexamples, catheter 10 may be configured such that conductors 48 and 50are independently coupled to one or more electrodes 24. In suchexamples, processing circuitry 76 may control electrical signalgenerator 78 to generate and deliver multiple electrical signals viadifferent combinations of conductors 48 and 50 and/or electrodes 24. Inthese examples, energy source 70 may include a switching circuitry toswitch the delivery of the electrical signal using electrodes 24, e.g.,in response to control by processing circuitry 76.

Power source 80 delivers operating power to various components of energysource 70. In some examples, power source 80 may represent hard-wiredelectrical supply of alternating or direct electrical current. In otherexamples, power source 80 may include a small rechargeable ornon-rechargeable battery and a power generation circuit to produce theoperating power. Recharging may be accomplished through proximalinductive interaction between an external charger and an inductivecharging coil within energy source 70.

A control mechanism 72, such as foot pedal, handheld, or remote-controldevice, may be connected to energy source 70 to allow the clinician toinitiate, terminate and, optionally, adjust various operationalcharacteristics of energy source 70, including, but not limited to,power delivery. Control mechanism 72 can be positioned in a sterilefield and operably coupled to the energy source 70 and can be configuredto allow the clinician to selectively activate and deactivate the energydelivered to one or more electrode 24. In other embodiments, controlmechanism 72 may be built into hub 14.

In some examples, cavity 22 may be formed using a single balloon withone or more electrodes positioned over the balloon configured torestrict the inflation of the balloon, thereby forming the respectivecavities. FIG. 8 is a schematic side view of another example catheter90, which includes an elongated member 92 extending from proximal end92A to distal end 92B. The side view of FIG. 8 is shown along alongitudinal axis 93 of elongated member 92.

Catheter 90 includes a hub 94 connected to proximal end 92A of elongatedmember 92. Hub 94, including proximal end 92A of elongated member 92,forms part of a proximal portion 96A of catheter 90. Catheter 90 alsoincludes a distal portion 96B that includes distal end 92B of elongatedmember 92. The various components of catheter 90 including, for example,hub 94, supply tubes 106, elongated member 92, and the like may besubstantially similar to the components of catheter 10 described aboveapart from any differences described below.

FIG. 9 is an enlarged conceptual cross-sectional view of distal portion96B of catheter 90 of FIG. 8, the side view illustrating distal portion96B along longitudinal axis 93 of elongated member 92. FIG. 9 showsdistal portion 96B deployed within vessel 30 of a patient, vessel 30including a target treatment site 32 containing a calcified lesion 34 onor within a wall of vessel 30.

As shown in FIG. 9, distal portion 96B of catheter 90 includes a balloon98 mechanically connected to elongated member 92 and configured to beinflated to an expanded state to occlude vessel 30 within thevasculature of a patient. Distal portion 96B also includes at least oneelectrode 100 carried by elongated member 92 and positioned over balloon98. Each electrode 100 is configured to restrict the expansion ofballoon 98 to cause balloon 98 to form a pair of balloon lobes (e.g.,first lobe 102A and second lobe 102B, referred to collectively as“balloon lobes 102”) when balloon 98 is inflated to the expanded state.Each pair of balloon lobes (e.g., first lobe 102A and second lobe 102B)define a cavity 104, which is a closed cavity when the respective pairof balloon lobes 102 contact a wall of the vessel 30 in the expandedstate. Each respective electrode 100 has at least one surface exposed tofluid 36 received within cavity 104 formed by the respective pair ofballoon lobes 102. The configuration of balloon 98 and electrode 100 mayhelp center electrode 100 within vessel 30, which may help ensure a moreequal distribution of the pressure pulse wave against the wall of vessel30 during the cavitation process as well as reduce the chance oflocalized heating along the wall of vessel 30 by electrode 100.

Catheter 90 may include any suitable number of balloon lobes 102 andelectrodes 100. In some examples, the total number of balloon lobes 102and electrodes may depend on the size and length of lesion 34 to betreated. Balloon lobes 102 and electrodes 100 may be any suitable sizeand length. In some examples, each electrode 100 may define a lengthalong longitudinal axis 93 of about 1 mm and each lobe 102 may define alength along longitudinal axis 93 of about 3 mm to about 4 mm, however,other lengths may also be used. In some examples, the length ofelectrode 100 may be adjusted to increase or decrease the resultant sizeof respective cavities 104.

FIG. 10 is an example side view of electrode 100 taken through line B-Bof FIG. 9. In some examples, electrode 100 may include a concentricelectrode (e.g., similar to concentric electrode 24A described abovewith respect to FIGS. 3A and 3B) positioned over balloon 98 to partiallyrestrict the inflation of balloon 98. While electrode 100 is primarilyshown and described as being a concentric electrode, other electrodeconfigurations (e.g., those shown and described in FIGS. 4-6) may alsobe used.

Electrode 100 may include an inner and outer conductive band 110 and 112respectively separated by an electrically insulative layer 114. Innerand outer conductive bands 110 and 112 may each be electrically coupledto a respective electrical conductor (e.g., electrical conductors 116)that extends along elongated member 92. Electrode 100 may define anelectrode aperture 118 of any suitable size and shape (e.g., hole orring) that passes through outer conductive band 112 and electricallyinsulative layer 114 to provide fluid communication between inner andouter conductive bands 110 and 112 (e.g., via fluid 36). Conductivebands 110 and 112 may have any suitable length. In some examples, eachconductive band 110 and 112 may comprise a ring or cylindrical body thatdefines a longitudinal length of about 1 mm. In some such examples,balloon 98 may define a length of about 25 mm to about 100 mm, butlength of balloon 98 may be increased or decreased depending on thetotal number of electrodes 100 and length of target treatment site 32.

During the cavitation procedure, an electrical signal may be deliveredbetween inner and outer conductive bands 110 and 112 using fluid 36captured within electrode aperture 118. The electrical signaltransmitted may form a corona, an electrical arc, a spark, or the likebetween the pair inner and outer conductive bands 110 and 112 usingfluid 36 as a conductive media to cause fluid 36 to undergo cavitation.The electrical signal transmitted and received between inner and outerconductive bands 110 and 112 may be delivered to electrode 100 from anenergy source (e.g., energy source 70) using electrical conductors 116.

As described further below, in some examples, electrical conductors 116may extend from proximal portion 96A of catheter 90 to electrode 100.Electrical conductors 116 may pass either eternal to balloon 98 asillustrated in FIG. 9 or pass through an interior portion of balloon 98,such as through a sidewall of the balloon or through relatively smallholes in balloon 98 to allow to electrically couple to one or moreelectrodes 100 to electrical conductors 116. The holes in balloon 98 maybe occupied by the electrical conductor(s) 116, such that little to noinflation fluid escapes from balloon 98 when balloon 98 is inflated andballoon 98 is able to remain inflated at the desired pressure during amedical procedure. Additionally, or alternatively, balloon 98 mayinclude an electrically conductive material embedded within the(electrically insulative) sidewall of the balloon (e.g., small gaugewire or a conducive polymer) to transmit the electrical signal betweenelectrode 100 and electrical conductors 116, or between two or moreelectrodes 100.

A proximal portion of electrical conductors 116 (e.g., the portion ofelectrical conductors 116 proximal to balloon 98) may extend along theexterior of elongated member 92, secured to or within elongated member92 (e.g., secured via a heat shrunk outer jacket), or may passed alongan inner lumen of elongated member 92. In some examples, the proximalportion of electricals conductors 116 may be braided or coiled aroundelongated member 92 and subsequently unbraided or uncoiled as theelectricals conductors 116 pass along balloon 98. A proximal end ofelectrical conductors 116 may be electrically connected to an energysource (e.g., energy source 70 of FIG. 7) in order to electricallyconnect electrode 100 to the energy source. In some examples wheredistal portion 96B includes a plurality of electrodes 100, eachcontained within a different cavities 104, each electrical conductor 116may be coupled to a respective electrode 100 to provide independentactivation to each electrode 100. In some such examples, at least one ofelectrical conductors 116 may serve as a common conductor (e.g.,reference wire) for each electrode 100.

In the respective expanded state within vessel 30, the various balloonlobes 102 of balloon 98 inflate and conform to engage with the wall ofvessel 30. In some examples, balloon 98 may be inflated via an inflationlumen 108 accessed by one of supply tubes 106 by the introduction of asaline or contrast solution. In some examples, one or more of balloonlobes 102 may include a perfusion port 110 that may be used to fill oneor more of cavities 104 with fluid 36. Perfusion port 110 may be used toresupply fluid 36 or continuously supply fluid 36 to a respective cavity104 during the cavitation process. In some examples, perfusion port 110may be sized to introduce fluid 36 into cavity 104 at a flow rate ofabout 1 mL/min to about 10 mL/min, when balloon 98 is inflated to apressure of about 2-6 atmospheres.

Balloon 98 may be formed from any suitable material, such as, but notlimited to, a flexible polymeric material that forms a tight seal withelongated member 92. In some examples, balloon 98 may be configured tobe deflatable via a vacuum or other stable source to forcibly removefluid from the balloon (e.g., remove fluid at about 1 mL/min).Additionally, or alternatively, balloon 98 may be a wrapped balloondefining a plurality of pleats 112 that are configured to be wrappedaround elongated member 92 while balloon 98 is in a collapsed state.

FIGS. 11A-11C are schematic views of an example wrapped balloon 120 in acollapsed (uninflated) state. FIG. 11A is a side view and FIGS. 11B and11C are cross-sectional views of wrapped balloon 120 along cross sectionC-C of FIG. 11A showing different ways electrical conductors 116 may beincorporated along the exterior of wrapped balloon 120 while in thecollapsed state. The cross-section is taken through one of respectiveballoon lobe areas (e.g., second lobe 102B) which does not include anelectrode. Wrapped balloon 120 may be used as balloon 98.

As shown in FIGS. 11B and 11C, wrapped balloon 120 defines a pluralityof pleats 122, which are wrapped (e.g., folded) around elongated member92A. Each pleat 122 may be wrapped in the same direction such thatpleats 122 may be laid on top of one another around the outer perimeter(e.g., a circumference if circular in cross-section) of elongated member92A.

FIG. 11B and 11C illustrate different techniques for how electricalconductors 116A and 116B may be incorporated along the exterior ofwrapped balloon 120 while the balloon is in a collapsed state. FIG. 11Bshows that electrical conductors 116A can be positioned adjacent to theapex 124 of each pleat 122, while FIG. 11C shows electrical conductors116B disposed within the inner folds 126 of each pleat 122. Theconfiguration of electrical conductors 116A in FIG. 11B may allow theone or more electrodes (e.g., electrode 100) to be assembled overwrapped balloon 120 after balloon 120 has been attached and wrappedaround elongated member 92A, while the configuration of electricalconductors 116B in FIG. 11C may help to at least partially protectelectrical conductors 116B while wrapped balloon 120 is being navigatedthrough the vasculature of the patient. In both cases, electricalconductors 116A and 116B may include sufficient slack to allow for theexpansion of wrapped balloon 120 without being decoupled from therespective electrode.

FIG. 12 is a flow diagram of an example technique of using catheters 10or 90 described herein. For illustrative purposes, the techniques ofFIG. 12 are described with reference to the various aspects of catheter10 or 90, however, such descriptions are not intended to be limiting andthe techniques of FIG. 12 may be used with other catheters or catheters10 and 90 may be used in other applications.

The technique of FIG. 12 includes introducing a catheter 10 throughvasculature of a patient and guide a distal portion 16B of catheter 10to a target treatment site 32 adjacent to a calcified lesion 34 (130),inflating one or more balloons to a respective expanded state to form acavity with the wall of vessel 30 (132). As described above, distalportion 16B may include a first and second balloons 18 and 20 connectedto elongated member 12 and separated by a distance such that such wheninflated to engage with vessel wall 36, first balloon 18 occludes aproximal portion of vessel 30 proximal to target treatment site 32 andsecond balloon 18 occludes a distal portion of vessel 30 distal totarget treatment site 32 to form cavity 22 that is exterior to the firstand second balloons 18 and 20. In other examples, the balloon mayinclude a single balloon (e.g., balloon 98) with the balloon beinginflated to form multiple balloon lobes 102 that form a cavity 104between adjacent lobes 102.

In some examples, first and second balloons 18 and 20 may beindependently expanded using different lumens to expand first and secondballoons 18 and 20. In some such examples, first and second balloons 18and 20 may be sequentially expanded in an order that follows thedirection of blood flow within vessel 30. For example, if blood flows inthe x-axis direction of FIG. 2, first balloon 18 may be inflated priorto inflating second balloon 20. In some examples, sequentially inflatingfirst and second balloons 18 and 20 in such a manner may assist withremoving blood from cavity 22 by allowing blood to continue to flow fromcavity 22 prior to second balloon 20 being inflated.

During or after first and second balloons 18 and 20 have been inflatedto engage vessel wall 36, cavity 22 may be filled with fluid 36 (134).In some examples, cavity 22 may be filled with fluid 36 using a lumen 38and access port 40 defined by elongated member 12 configured to provideaccess to cavity 22. Fluid 36 may include any suitable fluid capable ofundergoing a cavitation procedure. In some examples, cavity 22 may beaspirated (e.g., using lumen 38) prior to filling cavity 22 with fluid36 and/or after the cavitation procedure to remove fluid 36 and othermaterials from cavity 22 before deflating first and second balloons 18and 20.

The technique of FIG. 12 also includes delivering energy 48 to fluid 36within cavity 22 using at least one electrode 24 having at least onesurface exposed to fluid 36 (e.g., electrode 24 is positioned betweenthe first and second balloons 18 and 20 within cavity 22) to cause fluid36 to undergo cavitation to generate a pressure pulse wave within fluid36 (136). As described above, electrode 24 may transmit energy to fluid36 (e.g., electrical energy) that rapidly heats a portion of fluid 36 toproduce short-lived gaseous steam/plasma bubbles within fluid 36. Thesteam/plasma bubbles may represent relatively low-pressure pockets ofvapor generated from the surrounding fluid 36. The low-pressuresteam/plasma bubbles eventually collapse in on themselves due to therelatively high pressure of the surrounding fluid 36. As steam/plasmabubbles collapse, the bubbles release a large amount of energy in theform of a high-energy pressure pulse wave within fluid 36 that propagatethrough fluid 36 where they impact the wall of vessel 30 transmittingthe mechanical energy of the pressure pulse wave into the tissue ofvessel 30 and calcified lesion 34. The energy transmitted to calcifiedlesion 34 may cause the lesion to fracture or beak apart. In someexamples, this cavitation treatment of calcified lesion 34 may be usedin conjunction with either first or second balloon 18 and 20 to helpopen-up vessel 30 of the patient, restoring the vasculature to a normalor larger flow diameter. Additionally, or alternatively, this cavitationtreatment of calcified lesion 34 may be used in conjunction with POBA torestore the vasculature to a normal or larger flow diameter.

In some examples, the electrical energy delivered to fluid 36 via one ormore electrodes 24 may be in the form of a corona, an electrical arc, aspark or the like. The electrical signal may be a continuous wave signalor in the form of a plurality of pulses, and may have any suitableelectrical signal parameters for creating the cavitation. For example,the electrical signal may have an amplitude of about 500 volts (V) toabout 5000 V, a pulse width of about 1 microsecond to about 200microseconds, and a frequency of about 0.5 Hertz (Hz) to about 1000 Hz.

After the cavitation procedure using the technique of FIG. 12, first andsecond balloons 18 and 20 may be deflated and catheter 10 may bewithdrawn from vessel 30.

Various examples have been described. These and other examples arewithin the scope of the following claims.

What is claimed is:
 1. A catheter comprising: an elongated memberconfigured to be navigated through vasculature of a patient to a targettreatment site; a first balloon connected to the elongated member, thefirst balloon being inflatable to an expanded state to occlude aproximal portion of a vessel proximal to the target treatment site; asecond balloon connected to the elongated member, the second balloonbeing inflatable to an expanded state to occlude a distal portion of thevessel distal to the target treatment site, and wherein when the firstand second balloons are in the respective expanded states within thevessel, a cavity is defined between the elongated member and the targettreatment site, the cavity being exterior to the first and secondballoons; and an electrode comprising an electrically conductive bandattached to the elongated member, the electrode configured to beconnected to an energy source configured to deliver an electrical signalto a fluid within the cavity and in contact with the electrode to causethe fluid to undergo cavitation to generate a pressure pulse wave withinthe fluid.
 2. The catheter of claim 1, wherein the electrode comprises aconcentric electrode wherein the electrically conductive band forms anouter electrically conductive band, the concentric electrode furthercomprising an inner electrically conductive band separated from theouter electrically conductive band by an electrically insulating layer,an aperture extending through the outer electrically conductive band andthe electrically insulating layer to provide fluid communication betweenthe inner and the outer electrically conductive bands.
 3. The catheterof claim 1, wherein the electrically conductive band forms a firstelectrically conductive band on the elongated member, the firstelectrically conductive band having a first surface area exposed to thecavity, the catheter further comprising a second electrically conductiveband on the elongated member, the second electrically conductive bandhaving a second surface area exposed to the cavity, the first and thesecond electrically conductive bands configured to deliver an electricalsignal between the first and the second surface areas through the fluidwithin the cavity to cause the fluid to undergo cavitation.
 4. Thecatheter of claim 1, wherein the elongated member defines a lumen and atleast one port connecting the lumen to the cavity, wherein the lumen andthe at least one port are configured to at least one of perfuse thecavity with the fluid or aspirate the cavity.
 5. The catheter of claim4, wherein the lumen and the at least one port are configured to perfusethe cavity with the fluid and aspirate the cavity.
 6. The catheter ofclaim 1, wherein the elongated member the defines an inner lumenconfigured to receive a guidewire.
 7. The catheter of claim 1, furthercomprising an electrical wire that extends along the elongated member, asurface of the electrical wire being exposed within the cavity, theelectrical wire configured to be connected to the energy sourceconfigured to deliver an electrical signal between the surface of theelectrical wire and the electrode.
 8. The catheter of claim 7, wherein aplurality of surfaces of the electrical wire are exposed to the fluidwithin the cavity, each exposed surface of the plurality of exposedsurfaces forming an electrode.
 9. A catheter comprising: an elongatedmember configured to be navigated through vasculature of a patient to atarget treatment site; a first balloon connected to the elongatedmember, the first balloon being inflatable to an expanded state toocclude a proximal portion of a vessel proximal to the target treatmentsite; a second balloon connected to the elongated member, the secondballoon being inflatable to an expanded state to occlude a distalportion of the vessel distal to the target treatment site, and whereinwhen the first and second balloons are in the respective expanded stateswithin the vessel, a cavity is defined between the elongated member andthe target treatment site, the cavity being exterior to the first andsecond balloons; and an electrical wire that extends along the elongatedmember, the electrical wire defining a plurality of exposed surfaceswithin the cavity, each exposed surface of the plurality of exposedsurfaces forming a respective electrode, wherein the electrical wire isconfigured to be connected to an energy source configured to deliver anelectrical signal to a fluid within the cavity and in contact with theplurality of exposed surfaces to cause the fluid to undergo cavitationto generate a pressure pulse wave within the fluid.
 10. The catheter ofclaim 9, wherein the electrical wire comprises a first electrical wireand the plurality of exposed surfaces comprise a first plurality ofexposed surfaces, the catheter further comprising a second electricalwire that extends along the elongated member, the second electrical wiredefining at least one exposed surface within the cavity forming a returnelectrode, wherein the second electrical wire is configured to beconnected to the energy source configured to deliver the electricalsignal between the least one exposed surface of the second electricalwire and the plurality of exposed surfaces of the first electrical wireto cause the fluid to undergo cavitation.
 11. The catheter of claim 9,wherein the elongated member defines a lumen and at least one portconnecting the lumen to the cavity, wherein the lumen and the at leastone port are configured to at least one of perfuse the cavity with thefluid or aspirate the cavity.
 12. The catheter of claim 11, wherein thelumen and the at least one port are configured to perfuse the cavitywith the fluid and aspirate the cavity.
 13. The catheter of claim 9,wherein the elongated member the defines an inner lumen configured toreceive a guidewire.
 14. A method comprising: introducing a catheterthrough vasculature of a patient to a target treatment site, thecatheter comprising: an elongated member comprising a distal portionconfigured to be navigated through the vasculature of the patient; afirst balloon connected to the elongated member; a second balloonconnected to the elongated member and distal to the first balloon; andat least one electrode carried by the elongated member between the firstand second balloons; inflating the first and second balloons to anexpanded state, wherein the first balloon occludes a proximal portion ofa vessel proximal to the target treatment site and the second balloonoccludes a distal portion of the vessel distal to the target treatmentsite, wherein the first and second balloons in the respective expandedstates within the vessel form a cavity defined between the elongatedmember and the target treatment site, the cavity being exterior to thefirst and the second balloons; filling the cavity with a fluid; anddelivering energy to the fluid within the cavity using the at least oneelectrode to cause the fluid to undergo cavitation and generate apressure pulse wave within the fluid.
 15. The method of claim 14,further comprising repositioning the catheter and inflating the first orthe second balloon to expand the vessel after a pressure pulse wavetherapy has been performed by the at least one electrode.
 16. The methodof claim 14, further comprising aspirating the cavity formed by thefirst and second balloons after a pressure pulse wave therapy has beenperformed by the at least one electrode.